Sometimes it’s privately subsidized, too, such as when you go out to eat and your meal costs more because the restaurant provides free parking. People who don’t drive often pay higher prices subsidizing the people who do, which is something we should talk about more directly.
Same with credit cards.
A lot of the time the businesses don’t have an option to not have parking as it is enforced by zoning laws/regulations.
Though they can make that mandatory parking paid but often the social norm is for it to be free (at least for the first hour or two)